1. Field of the Invention
The present invention relates to touch panels and, particularly, to a carbon nanotube based touch panel.
2. Discussion of Related Art
Following the advancement in recent years of various electronic apparatuses such as mobile phones, car navigation systems and the like toward high performance and diversification, there is continuous growth in the number of electronic apparatuses equipped with optically transparent touch panels in front of their display devices such as liquid crystal panels. A user of any such electronic apparatus operates it by pressing a touch panel with a finger, a pen, or the like tool while visually observing the display device through the touch panel. A demand thus exists for such touch panels that are superior in visibility and reliable in operation.
At present, different types of touch panels, including a resistance-type, a capacitance-type, an infrared-type and a surface sound wave-type have been developed. Due to a higher accuracy and a low-cost of the production, the resistance-type touch panels have been widely used.
A conventional resistance-type touch panel includes an upper substrate, an optically transparent upper conductive layer formed on a lower surface of the upper substrate, a lower substrate, an optically transparent lower conductive layer formed on an upper surface of the lower substrate, and a plurality of dot spacers formed between the optically transparent upper conductive layer and the optically transparent lower conductive layer. The optically transparent upper conductive layer and the optically transparent lower conductive layer are formed of conductive indium tin oxide (ITO).
In operation, an upper surface of the upper substrate is pressed with a finger, a pen or the like tool and visual observation of a screen on the liquid crystal display device provided on a back side of the touch panel is allowed. This causes the upper substrate to be deformed, and the upper conductive layer to come in contact with the lower conductive layer at a position being pressed. Voltages are applied successively from an electronic circuit to the optically transparent upper conductive layer and the optically transparent lower conductive layer. Thus, the deformed position can be detected by the electronic circuit.
However, the ITO layer (i.e. the optically transparent conductive layer) is generally formed by means of ion-beam sputtering, and the method is relatively complicated. Furthermore, the ITO layer has poor wearability, low chemical endurance and uneven resistance in an entire area of the panel. Additionally, the ITO layer has a relatively low transparency. All the above-mentioned problems of the ITO layer makes for a touch panel with low sensitivity, accuracy, and brightness.
What is needed, therefore, is to provide a durable touch panel having high sensitivity, accuracy, and brightness.